Pennsylvania Hospital in Philadelphia, PA, Massachusetts General Hospital in Boston, MA and the University of Padua in Padua, Italy are three of the few medical institutions in the world with surviving operating structures of what name? These anachronistic structures were originally set up like an amphitheater where students stood on raised tiers and looked down below at a central operating table to observe a dissection, but today are used as lecture halls or museums.

Considering all the tissues and cells in your body, 25 million new cells are being produced each second.